Originally an Indomalayan species, Rattus rattus was widely introduced across the globe as a result of human activities. In Europe, it has been present since ancient times, and is found in most countries. The species is widespread and common throughout the Mediterranean region. The list of countries of occurrence where the species is introduced is incomplete.

Still found throughout south-east Asia; includes a complex of at least four distinct species; Rattus rattus sensu strictu originally from Western India and Pakistan, spread worldwide thence.